<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Document</title>
        <style>
            button{
                background-color: #fff;
                border: 1px solid #000;
                border-radius: 5px;
                padding: 5px 10px;
                cursor: pointer;
                transition: all .5s;
            }
            button:hover{
                background-color: #000;
                color: #fff;
            }
            button:hover::after{
                content: "hello";
            }
            h1{
                color: #000;
                font-style: italic;
            }
            p{
                line-height: 30px;
                /* 当前字号的倍数 */
                text-indent: 2em;
            }
            a{
                color: pink;
            
            }
       </style>
    </head>
    <body>
        <button>按钮</button>
        <h1>标题</h1>
        <p>段落</p>
        <a href="#">超lianjie </a>
    </body>
</html>